In fact the entire history of Physics consists of a progression of theories
that unify diverse phenomena. For example, Maxwell showed that static
electricity, (which gives you a jolt when you touch a doorknob after shuffling
across a carpeted floor in your bare feet), and magnetism (which causes compasses
to point towards the North) are two different manifestations of one and the same
phenomenon. With another amazing intuitive leap, based essentially on symmetry arguments,
Albert Einstein was able to reconcile Maxwell's theory of electromagnetism with Newtonian
mechanics: the resulting framework, special relativity, caused a total upheaval in our
understanding of the structure of space and time. I would love to be able to talk more
about this, but it would be the subject of a whole talk all on its own.
Towards the end of the talk I will tell you about
two other recent attempts at synthesis, but first on to the notion of symmetry.